The invention relates to a building material additive in the form of an aqueous dispersion, containing air void formers, retardants, plasticizers, accelerators, or the like, or a mixture thereof, as well as to a process for the preparation thereof.
Additives have for some time been mixed with building materials to improve processing and to influence the solidification behavior and solidification time. Although they have the same or a similar effect in the building material, these additives belong, in general, to widely differing categories of chemical substances. Frequently it is desirable to affect a building material in several ways with an additive, or mixture of additives. Difficulties often arise in reconciling the extent of the desired effects, so that compromises are necessary and some additives cannot reach full effectiveness. Some additive combinations are not possible because in direct contact with one another they are incompatible. In general, the effectiveness of the additives is proportional to the concentration used but the proportionality does not follow a linear dependence. If incompatible additives are utilized, the result will be undesirable because the additives will not be distributed in the building material with sufficient homogeneity and, as a consequence, the effect of the additives will be stronger in some places, whereas in other parts of the mixture their effectiveness will be too low. The effect of the additives is to a considerable extent temperature-dependent, so that various combinations have to be chosen depending upon the season and the mean outside temperature.
When air void formers are combined with other additives, one can observe that the stability of the air voids is impaired. This results in too low a content of air voids, which have in general a relatively large diameter, and unfavorable spatial distribution of the air voids because especially those located in the vicinity of the surface display a tendency to escape before the solidification process has taken place.
An object of the present invention is thus to find a building material additive in which the effectiveness of the active ingredients used will be enhanced.